1. Field of the Invention
The present invention relates to a method for fabricating a capacitor in a semiconductor device, and more particularly to a method for fabricating a capacitor in a semiconductor device using a cyclic Si3N4 (or SiOxNy)
2. Description of the Prior Art
As generally known in the art, as shown in FIG. 1, with regards a conventional N/O (Si3N4/SiO2) capacitor, an interlayer insulating layer 11 is deposited on a wafer (not shown) wherein several elements are constructed, and selective patterning of the interlayer insulating layer is performed to thereby form a contact hole (not shown) exposing a part of the semiconductor wafer.
Then, a contact plug 13 is formed in the contact hole (not shown), and a storage node 15 of a cylindrical shape, a concave shape, or another shape, is formed on the surface of the entire resultant structure, and an oxide layer on the surface of the storage node 15 is removed through a pre-cleansing process by using a HF solution.
Next, an Si3N4 thin layer 17 is deposited through an LPCVD process (an ONO second process), and an oxidation process (an ONO third process) is performed to thereby form an upper electrode 19, resulting in the accomplishment of production of the capacitor.
However, since the cell area decreases due to the decrease of design rule, it is required to reduce the thickness (Teff) of the dielectric so as to obtain necessary charging capacity.
With regard to the conventional N/O dielectric, since the oxidation resistance of the Si3N4 becomes seriously reduced at a thickness below 40 Å due to the LPCVD process, there occur problems in that elements of the semiconductor positioned below the capacitor, such as the storage node and a bit-line, are oxidized at the time of the third ONO process, and it is difficult to lower the thickness Teff of the dielectric below 45 Å, because the leakage current increases and the breakdown voltage decreases at thickness below 50 Å.